Motor vehicle emission analysis system

ABSTRACT

A vehicle emission analysis interface system for supplying a sample of a test vehicle&#39;s exhaust gases to the inlet of an analyzer for providing a quantitative measurement of selected pollutants includes an exhaust sample inlet port for receiving a sample of the exhaust gases. A high pressure inlet port is adapted to be connected to a high pressure source at the test facility. A chiller for lowering the temperature of incoming gas sample stream has an inlet connected to the sample inlet port and an outlet. The system further includes a zero air generator having an inlet and an outlet for supplying purified air for analyzer calibration purposes. A reverse purge valve is arranged to selectively connect the high pressure inlet port to the zero air generator inlet and the chiller outlet in series with the analyzer inlet or to connect the high pressure inlet port to the chiller outlet to purge the chiller and components which feed the exhaust gas sample to the chiller of pollutants in the gas sample of the last vehicle tested. Valving is also provided to direct air from the zero air generator to a fuel cap adaptor with the flow rate being measured to check the integrity of the fuel cap with respect to the leakage of pollutant fumes.

FIELD OF THE INVENTION

The present invention relates to a system for evaluating the principalair contaminants in the exhaust gas emissions of internal combustionengines installed in motor vehicles and more particularly to a systemwhich interfaces between an exhaust probe inserted in a vehicle'sexhaust pipe and an analyzer.

DESCRIPTION OF THE PRIOR ART

It is well known that the exhaust gases from motor vehicles are a primecause of air pollution. Over the years various states in the UnitedStates, as well as foreign countries, have required that all vehicleengines be tested periodically to determine the quantitative presence ofharmful contaminants such as unburned hydrocarbons (HC), carbon monoxide(CO), carbon dioxide (CO₂), nitric oxide (NO), and oxygen (O₂) in theexhaust gas stream. Standards are set at the state or federal level andvehicles in which the exhaust gases exceed the standards are required tobe repaired to correct the engine malfunction. The vehicles areconventionally tested in vehicle test stations which accommodate largenumbers of vehicles with a plurality of test lanes. One vehicle afteranother is tested in each lane.

Recently as a result of our increasing environmental concerns, the U.S.Environmental Protective Agency ("EPA"), under the mandate of the 1990Clean Air Standards Act, has required 38 major metropolitan areas, inthe United States, to reduce pollutants in motor vehicle exhaustemission by implementing inspection maintenance ("IM") programs. Thisrequires that a vehicle's exhaust gases be sampled and analyzed under asimulated loaded condition, i.e., run on a dynamometer to simulateacceleration and road load forces. California has been at the leadingedge in developing a program to comply with the EPA mandate.

Through its Bureau of Automotive Repairs ("BAR"), California developedtesting and repair specifications which met the EPA requirements andmany other states and foreign countries have followed suit in adoptingthe BAR program.

The BAR program has greatly expanded the need for emission testing andrepair facilities. This, in turn, has created a need for an accurate,reasonably priced, instrumentation system, capable of handling andanalyzing vehicle exhaust gases on a mass through put basis. Spacerequirements are also an important factor since existing repair shops,with their limited garage areas, will bear the bunt of the testing andanalysis work.

Analyzers capable of providing quantitative measurements of exhaust gaspollutants have been available for some time. However, to provide anaccurate measurement, the exhaust gas steam entering the analyzer mustbe preconditioned to remove water vapor and solid particles. Inaddition, the analyzers must be periodically calibrated usingcalibration gases with predetermined levels of the several pollutants.

A sample of the gas to be analyzed is obtained by inserting an exhaustprobe into the vehicle's exhaust pipe. A flexible hose is generallyconnected between the probe and the analyzer housing. A pump is utilizedto draw the sample of exhaust gases from the probe to the analyzerinstrumentation. It is important that the sample being analyzed not becontaminated with pollutants left over in the probe, the connecting hoseand the major conditioning elements (upstream from the analyzer) from aprevious vehicle's exhaust. To obviate this problem, prior art interfacesystems have simply continued to operate the exhaust gas pump during theinterval between the withdrawal of the probe from the exhaust pipe ofthe last vehicle tested to the insertion of the probe into the exhaustpipe of the next vehicle to be tested. While this technique may aid inreducing cross contamination between vehicles, it suffers thedisadvantage of impermeating the probe and hose with ambient air fromthe test facility which in all probability will include its own set ofpollutants.

To properly condition the exhaust gas sample for input into theanalyzer, it is necessary to remove the water vapor therefrom. Prior artinterface systems have generally utilized cryogenic gases, via suitableheat exchangers, to lower the temperature and drop the dew point of theincoming exhaust gas stream to thereby dehumidify the gas. While thistechnique is quite satisfactory, it requires containers of cryogenic gaswith their attendant expense and space requirements.

The analyzer must be periodically calibrated which requires theavailability of substantially pure air (as well as calibration gasescontaining preset levels of the several pollutants which are the subjectof the testing process). Typically the pure air is supplied from one ormore high pressure tanks to the analyzer to provide a true zeroreference point. The use of such tanks not only requires considerablespace, but adds to the overall testing costs.

In addition to checking for excess exhaust gas pollutants, it isadvisable and perhaps necessary (depending upon the applicable laws) tocheck the integrity of the fuel tank closure or cap since a faulty capcan allow vaporized unburned hydrocarbons to escape into the atmosphere.Typical exhaust gas analysis instrumentation does not provide any meansto accomplish this task.

There is a need for a vehicle emission analysis interface system whichovercomes the above shortcomings.

SUMMARY OF THE INVENTION

A vehicle emission test interface system, in accordance with the presentinvention, includes an exhaust inlet port for connection to an exhaustgas probe through a hose. The system further includes a high pressureair inlet port adapted to be connected to a high pressure air source. Achiller, preferably of the electronic type, for reducing the temperatureof the incoming exhaust gas sample, has an inlet and an outlet with theinlet being connected to the exhaust gas inlet port. A zero airgenerator, with an inlet and an outlet, provides relatively pure airunder a predetermined pressure for calibration purposes. A reversingpurge valve arrangement is connected in series relationship with thehigh pressure inlet port, the zero air generator inlet port, the chilleroutlet and the inlet of an analyzer. The purge valve is arranged toselectively connect the high pressure air inlet port to the zero airgenerator inlet and at the same time connect the chiller outlet inseries with the analyzer inlet port or to connect the high pressureinlet port to the chiller outlet. The former valve setting conducts asample of the vehicle exhaust gases to the analyzer while the lattervalve setting provides a reverse flow of air through the chiller, theexhaust probe hose and the exhaust probe to flush out any pollutantsremaining in such as components after the analysis has been made. Apressure regulator provides a low pressure in the outlet of the zero airgenerator.

Preferably the system includes a fuel tank access cap integrity testport which is adapted to be connected to a fuel cap adaptor through ahose or conduit. A fuel cap integrity test valve is connected in seriesrelationship with a low pressure gas source (preferably to the zero airgenerator outlet), a flow sensor and the fuel cap integrity test port.The flow sensor measures the rate of gas flow through the adaptor withthe vehicle fuel cap mounted thereon. Other features of the presentinvention are set forth in the description of the preferred embodiment.

The construction, operation and features of the present invention maybest be understood by reference to the following description taken inconjunction with the accompanying drawings in which like components aregiven the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a vehicle emission analysis system inaccordance with the present invention;

FIG. 2 is a pneumatic flow diagram of the system of FIG. 1 showing thenormal flow of a sampled exhaust gas to the analyzer instrumentation;and

FIG. 3 is a pneumatic flow diagram of a portion of the system of FIG. 1showing the flow of air in the purge condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2 an exhaust gas probe 10, adapted to beinserted into the exhaust pipe, of a vehicle (not shown) being tested,is connected to an exhaust gas inlet port 12 via a flexible hoseassembly 14. The port 12, as well as several other inlet and outletports to be described, are secured in bulkheads which form part of ahousing for the vehicle emission analysis system of the presentinvention. The entire interface system may conveniently mounted in oneor perhaps two drawers of a cabinet.

A chiller 16, for lowering the temperature of the incoming exhaust gassample and thereby lowering its dew point, has an inlet 16a connected tothe port 12. An outlet 16b of the chiller is selectively connected, viaa reverse purge solenoid controlled valve 18, to the inlet 20a of amoisture and particulate filter 20. The filter 20 comprises a moistureremoval section 20b and a particulate removal section 20c. See FIG. 2.The chiller is of the thermal electric type in which the flow ofelectricity through dissimilar metals causes heat to flow from oneregion, such as the heat exchange conduit through which the gas sampleis passing, to another region such as the atmosphere, as is well knownto those skilled in the art. The chiller drops the temperature of thegas sample stream to about 50° F.

A solenoid operated ambient air valve 22 selectively supplies an exhaustgas sample from the outlet 20d of the filter 20 or ambient air (forcalibration purposes) from an ambient air inlet port 24 (and filter 26)to the inlet of 28a of analyzer instrumentation 28 via a solenoidoperated three line calibration valve 30 and a pump 32 as will bedescribed in more detail. The ambient air valve includes a gas sampleinlet 22a connected to the outlet of the filter 20 and ambient air inlet22b connected to the filter 26. The pump 32 has a gas 32a inlet(connected to the ambient air valve outlet 22c) and an outlet for theexhaust gas sample stream as well as a water inlet 32c and outlet 32dfor removing the condensed moisture from the filter section 20b via anoutlet port 31.

The analyzer 28 is formed in three sections, i.e., a bench unit 28bwhich measures HC, CO₂, CO, an O₂ sensor 28c and NO sensor 28d. Theanalyzer output stream is exhausted to atmosphere via outlet ports 27and 29. A vacuum transducer or sensor 34 is connected in the linebetween the valve 22 and the gas inlet 32a of the pump 32 for detectingthe presence of a leak in the system upstream from the pump with theprobe 10 capped off.

The calibration valve 30 includes a gas sample inlet 30a and an outlet30b which are normally in fluid communication with each other to connectthe gas outlet 32b of the pump 32 to the analyzer inlet 28a. This valveis also arranged to selectively route calibration gases from high andlow calibration vessels 34 and 36, via gas calibration inlets 30c and30d, respectively, to the analyzer inlet 28a. The vessels 34 and 36contain high and low levels of the pollutants or contaminants,respectively. These vessels contain predetermined amounts, inparts/million, of the pollutants to be measured. Pressure regulators 37and 39 control the pressure (e.g., 1-3 psia) of the calibration gasesfrom the vessels 34 and 36, respectively.

The valve 30 is also arranged to selectively supply substantially pureair from the outlet 38a of a zero air generator 38 (for calibrationpurposes) via a fuel cap integrity test solenoid operated valve 40 and apurified air inlet 30e. The outlet from the zero air generator 38 isalso selectively routed by the valve 40 to a fuel tank closure capadaptor 42 via a hose or conduit 44, fuel cap integrity test port 46, aflow sensor 48 and a precision orifice or restrictor 50. The orifice 50provides an appropriate flow rate, say 60 cc/min., to the adapter. Afuel cap 51 of the vehicle being tested is secured to the adaptor 42during the integrity test. The flow sensor is preferably arranged toprovide a reading of about 20-100 cc/min.

The inlet 38b of the zero air generator receives air under pressure, viathe reverse purge valve 18, a pressure regulator 52, a filter 54, a highpressure air inlet port 56 and a high pressure air source, e.g., 110psia, (not shown) supplied, for example, by the testing facility. Thezero air generator includes an internal scrubber, such as an ionizer andone or more filters (not shown) for removing substantially allimpurities from the incoming air and a reserve cylinder 38a foraccumulating and maintaining the filtered air at a suitable pressurelevel. A pressure regulator 38d is also provided adjacent to and inseries with the outlet of the zero air generator to supply purified airat a low pressure, e.g., 1-3 psia, from outlet 38a. The zero airgenerator with its pressure regulator serves as a low pressure air (orgas) source for the fuel cap integrity test procedure. It should benoted that the pressure regulators 38d, 37 and 39 are preferably set toprovide a maximum output flow rate of about 2.5 liters/min. This ratecan, of course, vary depending upon the specific components utilized inthe system.

The reverse purge valve 18, in its normal mode of operation, channelshigh pressure air from the port 56 to the inlet 38b of the zero airgenerator and the exhaust gas sample stream from the outlet 16b of thechiller to the inlet 20a of the filter apparatus 20. In its purge mode,the valve 18 redirects air from the high pressure inlet port 56 throughthe chiller (outlet to inlet), the exhaust gas inlet port, the hoseassembly 14, and the exhaust probe 10 as is illustrated in FIG. 3. Thereverse purge valve includes a gas sample inlet 18a which is normallyconnected to the chiller outlet 16b, a gas sample outlet 18b, a highpressure inlet connected to the pressure regulator 52, and a highpressure outlet which is normally connected to the inlet of the zero airgenerator as is illustrated in FIG. 2.

A computer 60, such as a conventional PC, controls the operation of thevarious solenoid operated valves as is illustrated in FIG. 1. The PCreceives the test data from the analyzer representing the quantitativemeasurements of the several pollutants from the test vehicle's exhaustgas stream as well as the fuel cap integrity test flow rate. The datawill normally be supplied to 1) a monitor 62 for review by the operator,2) a printer 64 for providing a printed record of the test results, and3) to a remote station, such as a governmental agency, for entry into apermanent database.

By way of example only, the following off the shelf components may beused in the system:

    ______________________________________    Component            Manufacturer    ______________________________________    Analyzer Section 28b Sensors Corp.    Analyzer Section 28c Sensors Corp.    Analyzer Section 28d Sensors Corp.    Solenoid Valve 18    Miller Valve    Solenoid Valve 30    Honeywell    Solenoid Valves 22,40                         Spartan    ______________________________________

To prepare the system for operation, a high pressure source of air,e.g., compressed air, at the testing facility, is connected to the port56. The analyzer is then calibrated, if necessary, by sequentiallyrouting the calibration gases and/or ambient air and purified air to theanalyzer sections via valves 30, 22 and 40. The hose 14 and exhaustprobe may then be connected to port 12. The probe and hose may bechecked for leaks by capping the probe 10, operating pump 32 andchecking the degree of vacuum measured by the transducer 35.

The exhaust probe may then be inserted into the exhaust pipe of thevehicle to be tested and a sample of the vehicle exhaust gases routed tothe analyzer by operating the valves 18, 22 and 30 in their normal mode.The measured values will be compared with prescribed permissible valuesin the computer. Once the pollutants have been measured, the vehicle'sgas fuel cap may be secured to the adaptor 46 with the hose 44connecting the adaptor to the port 46. The solenoid valve 40 may then beactuated to divert the output air from the zero air generator throughthe restrictor 50, the flow sensor and the port 42. The measured flowrate will be compared with the permissible value, e.g., 60 cc/min., inthe computer. The exhaust probe may be removed from the vehicle'sexhaust pipe and readied for use with the next vehicle by operating thepurge reverse valve 18 to direct the high pressure air stream from theport 56 through the chiller, hose 14 and probe 10 in a directionopposite the direction of the exhaust sample stream.

Various modifications of the emission analysis system described abovewill become apparent to those skilled in the art without involving anydeparture from the spirit and scope of the invention as defined in theappended claims.

What is claimed is:
 1. In a vehicle emission analysis interface systemfor supplying a sample of a test vehicle's engine exhaust gases to aninlet of an analyzer for providing a quantitative measurement ofselected pollutants, the combination comprising:an exhaust gas sampleinlet port adapted to be connected to an exhaust gas probe through ahose for receiving a sample of the vehicle's exhaust gases; a highpressure air inlet port adapted to be connected to a high pressure airsource; a chiller having an inlet and an outlet for lowering thetemperature of the exhaust gases passing therethrough, the chiller inletbeing connected to the exhaust gas sample inlet port; a zero airgenerator having an inlet and an outlet for providing substantiallypurified air under a predetermined pressure in the outlet thereof; and areverse purge valve connected in series relationship with the highpressure inlet port, the zero air generator inlet, the chiller outletand the analyzer inlet, the purge valve being arranged to selectivelyconnect the high pressure inlet port to the zero air generator inlet andthe chiller outlet in series with the analyzer inlet or to connect thehigh pressure inlet port to the chiller outlet.
 2. The invention ofclaim 1 further including an ambient air inlet port and an ambient airvalve connected in series relationship with the analyzer inlet, thechiller outlet and the ambient air inlet port for selectively directingthe exhaust gas sample from the chiller outlet to the analyzer foranalysis of the same or directing ambient air to the analyzer forcalibration purposes.
 3. The invention of claim 1 wherein the testvehicle includes a fuel cap for providing access to the vehicles fueltank and further including:a fuel cap integrity test port adapted to beconnected to a fuel cap adaptor through a conduit; a flow sensorconnected to the fuel cap integrity test port for measuring fluid flowthrough the test port; a source of low pressure gas; and a fuel capintegrity test valve connected in series relationship with the lowpressure gas source, the flow sensor and the fuel cap test port forselectively directing air flow from the low pressure air source throughthe flow sensor, the fuel cap test port, and the conduit to the fuel capadaptor.
 4. The invention of claim 3 wherein the zero air generatorincludes a pressure regulator for providing a low pressure air stream inthe outlet and wherein the fuel cap test valve is connected between thezero air generator outlet and the flow sensor.
 5. The invention of claim1 further including a pneumatic pump connected in series relationshipbetween the gas sample inlet port and the analyzer inlet.
 6. Theinvention of claim 1 further including a condensed moisture removingfilter having an inlet and an outlet, the moisture removing filter beingconnected in series relationship between the chiller outlet and theanalyzer inlet.
 7. The invention of claim 6 further including acalibration valve having a gas sample inlet and an outlet, the outletbeing connected to the analyzer inlet, the gas sample inlet beingconnected in series with the moisture removing filter outlet, thecalibration valve further having at least one calibration gas inletadapted to be connected to a calibration gas source, the calibrationvalve being arranged to selectively connect the gas sample inlet or thecalibration gas inlet to the outlet thereof.
 8. The invention of claim 7further including an ambient air inlet port and an ambient air valve,the ambient air valve having a gas sample inlet, an ambient air inletand an outlet, the gas sample inlet of the ambient air valve beingconnected to the moisture removing filter outlet, the ambient air inletport being connected in series with the ambient air inlet of the ambientair valve, the outlet of the ambient air valve being connected in serieswith the analyzer inlet, the ambient air valve being arranged to routefluid from the moisture removing filter outlet or ambient air to theanalyzer.
 9. The invention of claim 8 including a pneumatic pumpconnected between the gas sample inlet of the calibration valve and theambient air valve outlet.
 10. The invention of claim 1 further includingmeans for measuring the degree of vacuum existing at the exhaust gassample inlet port.
 11. The invention of claim 7 wherein at least onecalibration gas inlet comprises two inlets with one inlet being arrangedto be connected to a high level pollutant source and the other inletbeing arranged to be connected to a low level pollutant source.
 12. Theinvention of claim 11 wherein the calibration valve further includes apurified air inlet and means for selectively connecting the zero airgenerator outlet to the purified air inlet.
 13. In a vehicle emissionanalysis system for providing an analysis of selected pollutantsemanating from an motor vehicle, the combination comprising:a gasanalyzer having an inlet for providing a quantitative measurement of theselected pollutants in a sample gas stream; an exhaust gas sample inletport adapted to be connected to an exhaust gas probe through a conduitfor receiving a sample of the vehicle's exhaust gases; a dehumidifierconnected in series relationship between the gas sample inlet port andthe analyzer inlet; a fuel cap integrity test port adapted to beconnected through a conduit to a fuel cap adaptor, the adaptor beingarranged to receive a fuel cap; a flow sensor connected to the fuel capintegrity test port for measuring the fluid flow therethrough; a sourceof low pressure gas; and a fuel cap integrity test valve connected inseries relationship with the low pressure gas source, the flow sensorand the fuel cap test port for selectively directing air flow from thelow pressure air source through the fuel cap test port.
 14. Theinvention of claim 13 further including:a zero air generator having anoutlet for providing substantially pure air at low pressure; a source ofat least one calibration gas; a calibration valve having an exhaust gassample inlet connected in series with the dehumidifier to receive thedehumidified gas sample, at least one calibration gas inlet connected tothe calibration gas source, a pure air inlet in series with the outletof the zero air generator and an outlet connected to the analyzer inlet,the calibration valve being arranged to selectively connect the gassample inlet, the calibration gas inlet or the pure air inlet to theoutlet thereof.
 15. The invention of claim 14 wherein the dehumidifierincludes a thermal electric chiller and a moisture removing filter, thechiller having an inlet and an outlet, the moisturizing filter beingconnected to the chiller outlet.
 16. The invention of claim 15 whereinthe zero air generator has an inlet and further including a highpressure inlet port adapted to be connected to a high pressure airsource and a reverse purge valve connected to the exhaust gas sampleinlet port, the high pressure air inlet port, the chiller inlet and thezero air generator inlet, the purge valve being arranged to connect thegas sample inlet port to the chiller inlet and the high pressure airinlet port to the zero air generator inlet or to connect the highpressure air inlet port to the chiller outlet.
 17. The invention ofclaim 16 wherein the dehumidifier has an outlet and further including anambient air inlet port, a pneumatic pump having an inlet and outlet andan ambient air valve having an inlet and an outlet, the outlet of thepneumatic pump being connected to the gas sample inlet of thecalibration valve, the ambient air valve being connected to dehumidifieroutlet, the ambient air inlet port and the pump inlet, the ambient airvalve being arranged to connect the dehumidifier outlet or the ambientair inlet port to the pump inlet.
 18. The invention of claim 17 whereinthe zero air generator comprises the source of low pressure gas.